The present invention relates to a data storage apparatus and a manufacturing method thereof. In particular, the invention relates to a mechanism which controls the protrusion of a head element section in a data storage apparatus and a manufacturing technique which facilitates the control.
As known, there are a variety of data storage devices which use different types of media such as optical disks and magnetic tapes. Among them, the hard disk drive (HDD) has become so popular as to be one of the indispensable storage devices for today's computer systems. Further, not limited to computers, the hard disk drive is widening its range of application more and more due to the superior characteristics, covering moving picture recording/reproducing apparatus, car navigation systems, cellular phones, removable memories for digital cameras and so on.
Each magnetic disk used in hard disk drives has a plurality of data tracks formed concentrically. In each data track, a plurality of data sectors are recorded which contain a plurality of servo data, including address information, and user data. A plurality of data sectors are recorded between servo data. Data can be written to and read from a desired data section by a head element section of a head slider held on an actuator which is swung to access the data section according to the address information of the servo data.
During operation, the head slider forms a spacing in the order of several or several ten nanometers between it and the magnetic disk by using the air flow which is caused by the rotating magnetic disk. To allow the head slider to stably hover or glide, the magnetic disk should have a flat and smooth surface. In order to realize high recording density, however, tiny bumps are formed on the magnetic disk surface. It is difficult to form these tiny bumps uniformly in height. That is, it is difficult to completely remove abnormally high bumps.
In the case of a head element section using a magnetoresistive effect transducer, if an abnormally high bump touches the head element section, this contact raises the temperature of the element section due to frictional heat, which temporally changes the resistance and therefore causes an abnormality in the read signal. This abnormality is called a Thermal Asperity (TA). Further, it is possible that the magnetic head itself may be damaged if the magnetic head makes harsh contact with a tiny bump.
As a solution to this problem, a magnetic disk drive is disclosed in Patent Document 1 (Japanese Patent Laid-open No. 10-269527). A head slider mounted in the magnetic disk drive is characterized in that a head element section formed by thin film process technology is recessed from the head slider surface so as to depart more from the magnetic disk. That is, this technique forms a recessed head element step on the slider in order to prevent the magnetic head from making contact with tiny bumps on the magnetic disk.
In terms of magnetic read/write, however, this technique causes more deterioration in performance if the recession of the device element section is enlarged since the clearance between the head device section and the magnetic disk becomes larger although thermal asperities can be suppressed. Enlarging the recession does not simply mean a better result.
As a solution in terms of both head failure and performance, a head slider is disclosed in Patent Document 2 (Japanese Patent Laid-open No. 2003-272335). In addition to a write device and a read device, the head element section of this head slider has a thermal expansion element and a contact detector near the read and write devices. Further, the head element section is recessed in advance from the slider surface which faces the magnetic disk. In the magnetic disk drive, as necessary for write or read, electricity is supplied to the thermal expansion element to expand the element. This makes the head element section closer to the magnetic disk. If the expansion is excessive, the head element section may protrude beyond the slider surface faced toward the magnetic disk. In this case, it is possible that the head device section may make contact with tiny bumps on the magnetic disk. So as to avoid contact with tiny bumps due to excessive protrusion, the amount of electricity supplied to the thermal expansion element is adjusted according to the spacing detector.
This technique makes it possible to prevent the head element section from making contact with tiny bumps on the magnetic disk while controlling the spacing between the head element section and the magnetic disk. However, head sliders which are actually mounted in data storage apparatus have different flying characteristics. Furthermore, the recession of the head element section differs among the head sliders.
In addition, in a comparison between a head slider having a small recessed head element step on a slider and a large flying height and a head slider having a larger recessed head element step on a slider and a small flying height, it is more difficult for the former than the latter to judge whether the head element section is protruded beyond the slider surface faced toward the magnetic disk when the thermal expansion element is energized and expanded for write or read.
Therefore, this technique is not effective for new bumps grown from defects on the magnetic disk and dust particles inhaled between the head slider and the magnetic disk during the operation of the magnetic disk drive. The risk of the head element section being damaged by contact with such bumps and particles is not yet eliminated.